George's quote is accurate, Michelin says 6 years.
The best way to store tires is in a cool, dry place, devoid of light, and on their sidewalls.
On one side of a tire you'll find a D.O.T. stamp indented into the sidewall. It should be 4 numbers long. An example is: 2605, this would be the 26th week in the year '05. I'm pretty sure that's the way all tire manufacturers do it, but I could be wrong.
Michael
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